1. Technical Field
The present invention relates to a method of detecting a sheet in a transport device that transports, for example, a sheet, an image reading device that reads an image recorded on a sheet transported by a transport device, and an image forming apparatus that records an image read by the image reading device.
2. Related Art
In general, there is known a complex machine as an image forming apparatus that has a transport function for transporting a sheet used as base paper, a reading function for reading an image of the transported sheet, and a recording function for recording the read image on a recording sheet or the like. In the complex machine, a plurality of sheets is set to be stacked in a set section and the sheets are sequentially transported one by one. Further, the set section is provided with a sheet sensor that can detect whether a sheet exists or not. Accordingly, when all the sheets set in the set section are transported and do not exist, the nonexistence of the sheet is detected by the sheet sensor.
In the past, a sensor (hereinafter, referred to as a “sensor in the related art”) disclosed in, for example, JP-UM-A-5-32347, has been widely employed as the sheet sensor. The sensor includes a detection lever of which the end freely extends back and forth to the sheet set face of the set section, and the detection lever is pushed so that the end of the detection lever always protrudes upward from the set face. Further, the sensor in the related art detects whether a sheet exists or not by whether a sheet stacked on the set face of the set section presses the end of the detection lever in a retracting direction.
However, in the above-mentioned sensor in the related art, if there is warping or a wrinkle on the sheet set in the set section and the sheet is thus deformed, when the position of a portion having warped or the wrinkle corresponds to the detection lever, the end of the detection lever is not pressed by the sheet or a pressing force of the sheet becomes insufficient. For this reason, in that case, there is a problem as follows: there is a false detection that the sheet set in the set section does not exist even though there are sheets remaining in the set section.